1. Field of the Invention
The present invention relates generally to image formation apparatuses and particularly to image formation apparatuses having a function detecting the amount of waste toner in a waste toner accommodation unit.
2. Description of the Related Art
Laser printers, copiers, multi function peripherals (MFPs) having their functions combined together, and other similar image formation apparatuses that fix toner on a printing sheet for printing have a photoreceptor drum, and an intermediate transfer belt. On the surfaces of such members, toner, and a carrier (a 2-component developing agent), which will hereinafter generally be referred to as waste toner, remain. Such waste toner is removed with a cleaner blade and accommodated in a waste toner accommodation unit, which is referred to as a waste toner box, for recovery. When the waste toner accommodation unit becomes full of waste toner, the waste toner accommodation unit is emptied or exchanged for disposal. Accordingly, to implement an apparatus reduced in size, improved in serviceability, inexpensive, and the like, it is important to optimize the amount of waste toner in the waste toner accommodation unit. To do so, an image formation apparatus is provided with a function detecting the amount of waste toner. When the amount of waste toner in the waste toner accommodation unit reaches a maximum accommodatable amount, an indication or the like is displayed to exchange the waste toner accommodation unit.
Conventionally the amount of waste toner in a waste toner accommodation unit is detected generally by a function configured to utilize an optical sensor to detect the toner's liquid level. FIGS. 7A and 7B are diagrams schematically showing a waste toner accommodation unit for illustrating a specific example of a configuration utilizing an optical sensor to detect toner's liquid level to detect the amount of waste toner in the waste toner accommodation unit, as conventional. The figures show a waste toner accommodation unit 1, which is assumed to be placed in the longitudinal direction of a cylindrical photoreceptor drum (not shown), (i.e., in the direction of the cylinder), and FIG. 7A schematically shows waste toner accommodation unit 1 as seen in a direction parallel to the longitudinal direction of the photoreceptor drum and FIG. 7B schematically shows the same as seen from cross section VIIB-VIIB in the direction of an arrow VIIB indicated in FIG. 7A.
With reference to FIGS. 7A and 7B, waste toner accommodation unit 1 as seen in its longitudinal direction has one side (a left side in FIG. 7B) provided with toner drop ports 2A and 2B. A cleaner blade 3A recovers residual waste toner on a surface of the photoreceptor drum, and an intermediate transfer belt. The recovered waste toner is dropped through toner drop ports 2A and 2B to waste toner accommodation unit 1 for recovery.
With reference to FIG. 7B, waste toner accommodation unit 1 as seen its longitudinal direction has a side remote from toner drop port 2B (a right side in FIG. 7B) provided with a liquid level detection unit 6 utilizing an optical sensor 6C. Optical sensor 6C emits light, which is in turn guided by an emission-associated light guide 6A and thus emitted in waste toner accommodation unit 1 parallel to the longitudinal direction of waste toner accommodation unit 1, and passes through a photoreception-associated light guide 6B and is thus received by optical sensor 6C. Liquid level detection unit 6 detects transmittance from the quantities of light emitted and received, respectively, by optical sensor 6C, and thus detects that the liquid level of the waste toner accommodated in waste toner accommodation unit 1 has passed across a position of light emission from emission-associated light guide 6A.
However, such a result of detection provided by such conventional method of detecting an amount of waste toner is affected by the state of the liquid level of the toner. For example, if the waste toner accommodation unit is inclined, the toner has a liquid level inclined relative to the waste toner accommodation unit. Furthermore, if waste toner is not accommodated in the waste toner accommodation unit uniformly, it has an uneven liquid level. This results in a varying liquid level detection and thus prevents detecting the correct amount of the waste toner. Conventionally, such disadvantage has been handled by a waste toner accommodation unit having a capacity provided with a margin for accommodating toner, an image formation apparatus provided with an arrangement that levels toner's liquid level, and the like. In the FIGS. 7A and 7B example, waste toner accommodation unit 1 internally has a toner transporting rotation members 4A and 4B having a surface with an agitation fin in the form of a screw and extending in the longitudinal direction to be rotated by a gear 5, which serves as a rotation mechanism, in a direction indicated in FIG. 7A by an arrow. As toner transporting rotation members 4A and 4B are rotated by gear 5, the agitation fin in the form of the screw that is provided on a surface thereof moves rightward or leftward the waste toner dropping through tone drop ports 2A and 2B, shown in FIG. 7B at a left side, and thus accommodated, and agitates the waste toner in waste toner accommodation unit 1.
The method utilizing an optical sensor to detect a liquid level is also disadvantageous in that a resultant detection is affected by an emission unit and a photoreception unit that are soiled. More specifically, the emission and photoreception units are located at a position facing waste toner. When the emission and photoreception units have their surfaces soiled with waste toner, they contribute to detection with reduced precision and prevent detecting a correct amount of waste toner. This disadvantage has conventionally been handled by providing an image formation apparatus with a configuration cleaning the emission and photoreception units. In the FIGS. 7A and 7B example, a portion of toner transporting rotation member 4A that immediately underlies emission-associated light guide 6A and photoreception-associated light guide 6B has a light guide cleaner 7 in the form of a plate connected thereto. Light guide cleaner 7 as seen in the longitudinal direction of toner transporting rotation member 4A has a length equal to the distance from emission-associated light guide 6A to photoreception-associated light guide 6B, and as seen in a direction orthogonal to the longitudinal direction of toner transporting rotation member 4A has a length equal to the distance from toner transporting rotation member 4A to emission-associated light guide 6A and photoreception-associated light guide 6B. As toner transporting rotation member 4A rotates, light guide cleaner 7 rotates with toner transporting rotation member 4A serving as an axis of rotation. In doing so, it passes between emission-associated light guide 6A and photoreception-associated light guide 6B, and thus contacts a surface of emission-associated light guide 6A and that of photoreception-associated light guide 6B to clean them.
A conventional image formation apparatus that has such a configuration as above has a disadvantage, i.e., a miniaturized, simplified and inexpensive image formation apparatus cannot be achieved.